Apparatus for producing oxygen of high purity



June 30, 1936. a. J. BOSHKOFF 2,046,284

APPARATUS FOR PRODUCING OXYGEN OF HIGH PURIfIY Original Filed May 18,1933 2 Sheets-Sheet 1 INVENTOR June 30, 1936. G. J. BOSHKOFF 2,046,284

APPARATUS FOR PRODUCING OXYGEN OF HIGH PURITY Original Filed May 18,1935 2 Sheets-Sheet 2 INVENTOR Patented June 30, 1936 HIGH PURITY GeorgeJ. Boshkofi, Buflalo, N. Y., assignor, by

mesne assignments, to Union Carbide and Carbon Corporation, acorporation of New York Original application May 18, 1933, Serial No.

671,690, now Patent No. 1,985,763, dated December 25, 1934.

Divided and this application August 22, 1934, Serial No. 740,902

5 Claims.

This invention relates to apparatus for producing oxygen of high purityand more particularly oxygen in the liquid phase free from high boilingpoint materials.

The invention has for its object generally, the provision of improvedapparatus whereby oxygen, especially liquid oxygen, may be readilyproduced in an easy and expeditious manner with rectifying apparatus,whether operated continuously or discontinuously, so as to besubstantially free from impurities of the character indicated.

More specifically, it is an object to provide apparatus for themanufacture of oxygen whereby it is produced substantially free fromsmall amounts of hydrocarbons and rare gases ordinarily present in theincoming air, which is employed as the raw material from which theoxygen is to be separated.

It is also an object to provide gas separating apparatus withrectification chambers or columns so arranged that substantially pureoxygen is separated by fractional condensation and evaporation withoutcontamination with undesired high boiling point materials and withoutinterfering with the stability and operative balance in the cyclicoperations taking place in the rectification columns or chambers.

It is also an object to provide an additional column or chamber inrectification apparatus which is to be operated in conjunction with theusual second or last chamber of ordinary twocolumn apparatus.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of elements,-

and arrangement of parts, which will be exemplified in the constructionhereinafter set forth and the scope of the application of which-will beindicated in theclaims.

This application is'a division of my application Serial No. 671,690,filed May 18, 1933, issued as Patent No. 1,985,763, granted December 25,1934.

For a fuller understanding of the nature and objects of the inventionreferences should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

Fig. 1 is a fragmentary vertical sectional view showing somewhatdiagrammatically a rectification apparatus constructed in accordancewith the invention; and

Fig. 2 is a similar view showing a modified arrangement in which theadded column, provided in accordance with the invention, is operatedseparately.

In the manufacture of oxygen for industrial use, it is customary toemploy air as the raw material and to separate the oxygen from the airin one or more stages by the rectification of liquid air, theatmospheric air having been compressed and cooled by heat exchangers andexpaneled in various stages by steps well known to the art. There are inair, as is well known, certain gas materials of high boiling point whichfrequently comprise undesirable impurities in oxygen obtained in thismanner. Also, where oxygen is to be provided for industrial use, verysmall amounts of certain hydrocarbons and other 15 undesirable gases maybe present as impurities. By the present invention, these relativelyhigh boiling point materials are separated from the liquid oxygen bysteps which do not require the input of any more power than is nowcustomarily employed in the operation of the usual rectification cycle.

In the practice of the present invention, the step of rectifying thegaseous mixture in the low pressure rectifying column or chamber isper-' formed in two stages carried out successively. This isadvantageously achieved by dividing the low pressure rectifying chamberor column into two parts and operating them in series. This divisionpreferably afiects what would ordinarily be the lower two-thirds of thelow pressure rectiiying column of a two-column rectifying apparatus.

Referring now to the drawings and particularly to Fig. 1, l denotesgenerally the high pressure column or chamber of a rectifying apparatusinto which the gaseous mixture to be separated is introduced in a cooledstate through the conduit II, the cooling being carried outin anywell-known manner, for example, by means of expansion or passage throughheat interchangers, or both. This column is also provided with suitabledephlegmating means, for example, perforated partitions l2. The lowerend l3 of this column serves as a kettle in which liquid collects andboils, the more volatile products passing upwardly in the column. Fromthis kettle the conduit l4 leads to a distributing head l5 disposed inthe upper portion of a low pressure chamber or column l6 preferablydisposed above the high pressure chamber .lll. In the lower end of thissecond chamber is disposed a condenser H which serves to receive thevolatile material arising from the chamber in, a substantial portionthereof being condensed and returned tomunicatesatitslowerendwiththechamberll just above the shelf. The chamberII is also provided with dephlegmating means, here shown aspartitions2l,similartothoseinchambers ill and it.

In order to vaporiae the liquid which collectsinthelowerendoi'chamberilinamannersimilar to that in chamber It, aheating coil is provided in this chamber and the uncondensed gaseousmaterial led oil by the conduit ll supplied thereto through a branchconnection II. The liquid obtained by conderkation in coil is suppliedby another conduit 26 to the distributing head 2!. Gaseous material,which is substantiallypure oxygen, is led oil. from the chamber I tochamber II through conduit 21, this conduit being provided with a branch21" for bleeding of! gaseous material when desired.

It is also desirable to transfer gas material from the upper portion ofchamber l 6 to an intermediate point in chamber 28. A conduit foreiIecting this is shown at 2'l'.- The uncondensable gas materials whichhave a very low boiling point, together with the maJor portion of thenitrogen, are preferably led oil. the top. of the chamber 20 by means ofa conduit here indicated at 28.."

In operation, when the gaseous mixture supplied to the chamber llthrough the conduit II is cooled compressed atmospheric air, liquidcollects in the kettle I; which becomes relatively rich in oxygen, sincethe more volatile constituents, such as nitrogen, are being continuallyboiled oil! and washed, the condensate being returned by counter washingor refluxing. The

oxygen content of the liquid which collects inthe kettle i3 becomesrelatively high, for example,from35to45percent. Whileitisseen that themore volatile constituents, that is, the low boiling point constituents,are continually 're-h moved. the high boiling point constituents whichinclude undesired impurities remain and are passed into the low presurechamber it by way of conduit It with the liquid transfu'red.

In the chamber it, the liquefied gas material of high oxygen contentcollects in the lower end and is heated,.whereby further volatileconstituentsareremoved; Aliquidofveryhighbxygen content, in results,,butstill includes the high boiling point impurities. The oxygen portion ishere vaporized without carrying oil! anyofthehlahbdlingpointimpurities,

Byoperatingthechamberllinserieswiththes chamberlt,agaseousmaterialcomprisingsub--stantiallypureoxygenfreefromhighboiling point impurities is withdrawnthrouah the conduit 21 and is by counter-current Theupper chamber 36also has dephlegmating washing, so as to collect about the coil II,substantially all the remaining volatile or low boiling point'materialbeing removed and withdrawn through the connection II. Gaseous materialis also conducted by conduit II from the upperportion oi. chamber it toa point near the upper portion oi chamber 20; theoxygen content thereoi,however, is substantially lower than the oxygen content oi the liquidintroduced into chamber." through conduit It. In consequence,substantially pure liquid oxygen may be withdrawn fromthe lower portionof this chamber through V the withdrawal connection 21. A withdrawalconnection *2! is advantageously. provided for the lower end of chamberit in order tocarry l away when desired the high boiling point impur-'ities which may collect.

In Fig. 2, a modiiled arrangement of apparatus for carrying out theprocms oi the present invention is shown in which the divided lowpressure chambers that are operated in series are showna's structurallyseparated. Here, a high pressure column or chamber is shown at 3|, towhich a cooled, compressed, gaseous mixture. is supplied through aconduit 8|. This chamber 35 has dephlegmating means 82 and a kettle IIat the lower end, from-which liquid comprising a concentrate ofoxygen iswithdrawn through a conduit 34 and supplied to a distributing head in alow pressure chamber or upper column '36 of atwo-column rectifyingapparatus. This apparatus may begenerally of conventional design, exceptthat the other chamber is shorter, as it is the lower two-thirds of theconventional upper chamber that is divided to provide a sec- 35 and lowpressure chamber ii separated as indicated from that at 86, jun arrangedto be operated in c'onJunction therewith.

In the lower end of the upper chamber 36 is disposed a condenser 31adapted to return condensate to-the lower'chamber l0. Uncondensed gasmaterial is withdrawn through the conduit 38 and supplied to the heattransfer means .45 disposed in the lower end oi the chamber 40.

means 39 and gas withdrawal connections d 41' which communicate withintermediate p0 ts in the chamber It.

Chamber has a distributing head ll and dephlegmating means 42, conduit43 being arranged to lead condensate of relatively high nitrogenconcentration from an upper shelf in the chamber 30 to the head ll. Aconduit 4: leads from the lower end of the heat transfer means 45 tosupply gas material, in this case,'condensate, to the head ll. A conduit48 leads from the top of the chamber It to convey away uncondensed, lowboiling point gas materials. 1

In operation, the apparatus shown in 2 operates similarly to that shownin ,Fig. '1. In vconsequence, a liquid having an increased concentrationof ongen collects in: the kettle 88 along with the undesired hilh'bolllng Point impurities. In the upper chamber 36, a liquid 05collectsabout the condenser 31, which is substantially pure oxygenbutior the high boiling point impurities whicharecontainedtherein;Theoxygen content is here vaporized and the gaseous omen and volatilematerials are conveyed by gen free of high boiling point impurities.This is withdrawn when desired through the conduit 49.

Since certain changes may be made in the above construction. anddifferent embodiments of the invention could be made wthout departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent, is:

1. Apparatus for producing oxygen substantially free from high boilingpoint material comprising in combination a high pressure rectifyingcolumn having a liquid space at its lower end and a gas space thereaboveprovided with dephlegmating shelves, a pair of low pressure rectifyingcolumns arranged tobe operated in series having liquid spaces at theirlower ends and gas spaces thereabove provided with dephlegmating shelvesinserted therein, a plurality of connections between the gas spaces ofsaid low pressure rectifying column, a connection leading from theliquid space of said high pressure column and arranged to discharge inthe gas space above the dephlegmating shelves of one of said lowpressure rectifying columns, a connection leading from a shelf in saidhigh pressure rectifying column arranged to discharge in the upperportion of the gas space of the other of said low pressure rectifyingcolumns, a condenser in the liquid space of said first-named lowpressure rectifying column arranged to receive uncondensed vapors fromsaid high pressure rectifying column, a condenser in the liquid space ofsaid second-named low pressure rectifying column arranged to receiveuncondensed vapors from said first-named condenser, and a connectionleading from said second-named condenser to the gas space above thedephlegmating shelves of said second-named low pressure rectifyingcolumn.

2. Apparatus for producing oxygen substantially free from high boilingpoint material, comprising, in combination, a high pressure rectifyingcolumn, a pair of low pressure rectifying columns, one of said lowpressure columns being provided with a vent, a pair of independentconnections leading from respectively diflerent points in the gas spaceof said high pressure column to substantially the same point in the gasspace of said vented low pressure column, another connection leadingfrom the liquid space of said high pressure column directly to the gasspace of the other of said low pressure columns whereby liquid fractionsmay be supplied thereto, a pair of condensers disposed respectively inthe liquid spaces of said low pressure columns and connected in seriesin one of said independent connections whereby uncondensed vaporsreceived therein from said high pressure column are successively cooledand supply the heat of fractionation to said low pressure columns, saidcondensers being arranged to pass the condensate resulting from saidcooling to the gas space of said vented low pressure column, and aplurality of common connections dispomd to eflect free commimicationbetween the gas spaces of said low pressure columns at relativelydifierent points.

3. Apparatus for producing oxygen substantially free from highboilingpoint material, comprising, in combination, a high pressure rectifyingcolumn, a pair of low pressure rectifying columns, one of said lowpressure columns being provided with a vent, a pair of independentconnections leading from respectively diiferent points in the gas spaceof said high pressure column to substantially the same point in the gasspace of said .vented low pressure column, another connection leadingfrom the liquid space of said high pressure column directly to the gasspace of the other of said low pressure columns whereby liquid fractionsmay be supplied thereto, heat exchanging means disposed in each of saidlow pressure columns and connected in series in one of said independentconnections leading to the gas space of said vented low pressure column,and common connections arranged to effect free communication betwen thegas spaces of said low pressure columns.

4. Apparatus for producing oxygen substantially free from high boilingpoint material, com prising, in combination, a high pressure rectifyingcolumn, a pairof low pressure rectifying columns, one of said lowpressure columns being provided with a vent, a pair of independentconnections leading from respectively different points in the gas spaceof said high pressure column to substantially the same point in the gasspace of said vented low pressure column, another connection leadingfrom the liquid space of said high pressure column directly to the gasspace of the other of said low pressure columns whereby liquid fractionsmay be supplied thereto, a pair of condensers disposed in the liquidspace of each of said low pressure columns and connected in series inone of said independent connections that lead to the gas space of saidvented low pressure column, and a common connection arranged to effectfree communication between the gas spaces of said low pressure colunms.

5. Apparatus for producing oxygen substantially free from high boilingpoint material, comprising, in combination, a high pressure rectifyingcolumn, a pair of low pressure rectifying columns, independentconnections leading from respectively di'flerent points in the gas spaceof said high pressure column to substantially the same point in the gasspace of one of said low pressure columns, another connection leadingfrom the liquid space of said high pressure column directly to the gasspace of the other of said low pressure columns, heat exchanging meansdisposed in each of said low pressure columns and connected in series inone of said independent connections whereby the uncondensed vapors.passing therein upply the heat of fractionation to said low pressurecolumns, and a common connection arranged to effect free communicationbetwen the gas spaces of said low pressurecolumns.

GEORGE J. BOSHKOFF.

